Validation of photon emission based signals using an energy window network in conjunction with a fundamental mode discriminator circuit

• US 5,475,219 A
• Filed: 10/26/1994
• Issued: 12/12/1995
• Est. Priority Date: 10/26/1994
• Status: Expired due to Fees

• Current Assignee: Neoprobe Corporation
• Original Assignee: Neoprobe Corporation
• Inventors: Olson, Karl W.
• Primary Examiner(s): Fields, Carolyn E.
• Assistant Examiner(s): Glick, Edward J.
• Application Number:
  US08/329,505
• Time in Patent Office: 412 Days
• Field of Search: 250/336.1, 250/369, 250/370.01, 250/370.13, 250/370.06
• US Class Current: 250/336.1
• CPC Class Codes: A61B 6/4258 for detecting non x-ray radiation, e.g. gamma radiation A61B6/037 takes precedence
• CPC Class Codes: G01T 1/161 Applications in the field of nuclear medicine, e.g. in vivo counting apparatus for radiation diagnosis A61B6/00

Abstract

A system for detecting photon emissions wherein a detector serves to derive electrical parameter signals having amplitudes corresponding with the detected energy of the photon emissions and other signal generating events. Two comparator networks are employed within an energy window defining function to develop an output, L, when an event based signal amplitude is equal to or above a threshold value, and to develop an output, H, when such signal amplitude additionally extends above an upper limit. Improved reliability and accuracy is achieved with a discriminator circuit which responds to these outputs L and H to derive an event output upon the occurrence of an output L in the absence of an output H. This discriminator circuit is an asynchronous, sequential, fundamental mode discriminator circuit with three stable states.

Claims

1. A system for detecting photon emissions, each occurring at an energy of interest within a range thereof, comprising:

a crystal detector assembly having an input confronting said photon emissions and responsive thereto to derive electrical parameter signals each having an amplitude corresponding with said energy of interest;

a first comparator network responsive to each said electrical parameter signal and having an output, L, when said signal exhibits a said amplitude of value above a threshold value;

a second comparator network responsive to each said electrical parameter signal and having an output, H, when said signal exhibits a said amplitude of value above an upper limit value;

an asynchronous, sequential, fundamental mode discriminator circuit responsive to said output, L, and said output, H, having three stable states a, b, and c, and having a no-event output condition when in a said stable state, said discriminator circuit transitioning from said state a to said state b upon the occurrence of said output, L, without the presence of said output, H, and transitioning from said state b to said state a to derive an event output upon the termination of said output, L, during state b, without the presence of said output, H; and

control means responsive to each derived said event output for effecting an evaluation thereof.

2. The system of claim 1 in which said discriminator circuit is responsive when in said stable state, b, to said output L and said output H to transition with a no-event output condition to said stable state, c.

3. The system of claim 1 in which said discriminator circuit is responsive when in said stable state b to said output, L, in the absence of said output H to remain in said stable state b.

4. The system of claim 1 in which said discriminator circuit is responsive when in said stable state b to said output H in the absence of said output L to transition with a said no-event output condition to said stable state c.

5. The system of claim 1 in which said discriminator circuit is responsive when in said stable state c to the termination of said outputs H and L to transition with a said no-event output condition to said stable state a.

6. The system of claim 1 in which said discriminator circuit is responsive when in said stable state c to said output H in the absence of said output L to remain in said stable state c.

7. The system of claim 1 in which said discriminator circuit is responsive when in said stable state c to said outputs L and H to remain in said stable state c.

8. The system of claim 1 in which said discriminator circuit is responsive when in said stable state c to said output L in the absence of said output H to remain in said stable state c.

9. The system of claim 1 in which said discriminator circuit is responsive when in said stable state a to the absence of said outputs L and H to remain in said stable state a.

10. The system of claim 1 in which said discriminator circuit is responsive when in said stable state a to said output H in the absence of said output L to transition with a no-event output condition to said stable state c.

11. The system of claim 1 in which said discriminator circuit is responsive when in said stable state a to said outputs L and H to transition with a said no-event output to said stable state c.

12. The system of claim 1 in which said discriminator circuit is responsive when in said stable state b to said outputs L and H to transition with a said no-event output condition to said stable state c;

and is responsive when in said stable state c to the termination of said outputs H and L to transition with a said no-event condition to said stable state a.

13. A system for detecting photon emissions, each occurring at an energy of interest within a range thereof, comprising:

a crystal detector assembly having an input confronting said photon emissions and responsive thereto to derive electrical parameter signals each having an amplitude corresponding with said energy of interest;

a first comparator network responsive to each said electrical parameter signal and having an output, L, of given pulse width when said signal exhibits a said amplitude of value above a threshold value;

a second comparator network responsive to each said electrical parameter signal and having an output, H, of pulse width substantially equal to said given pulse width when said signal exhibits a said amplitude of value above an upper limit value;

an asynchronous, sequential, fundamental mode discriminator circuit responsive to said output, L, and said output, H, having three stable states a, b, and c, and having an event output and a no-event output condition, and having said no-event output condition when in a said stable state, said discriminator circuit transitioning from said state a to said state b upon the occurrence of said output, L, without the presence of said output, H, responsive when in said stable state b to the occurrence of said output H in the presence of said output L to transition with a said no-event output condition to said stable state c, and responsive when in said stable state c to the termination of said outputs L and H to transition with a said no-event output condition to said stable state a; and

control means responsive to each derived said event output for effecting an evaluation thereof.

14. The system of claim 13 in which said discriminator circuit is responsive to transition from said stable state b to said stable state a to derive a said event output upon the termination of said output L without the presence of said output H, during said stable state b.

15. The system of claim 14 in which said discriminator circuit is responsive when in said stable state b to said output, L, in the absence of said output H to remain in said stable state b.

16. The system of claim 14 in which said discriminator circuit is responsive when in said stable state a to said output H in the absence of said output L to transition with a no-event output condition to said stable state c.

17. The system of claim 14 in which said discriminator circuit is responsive when in said stable state a to said outputs L and H to transition with a said no-event output to said stable state c.